What I'm really after is twin (or more) pot calipers as well as slightly lager discs.
Using larger discs (312mm will be 24mm larger in dia) will aid slowing down considerably. Think about a spinning bicycle wheel its easier to grab hold of and stop a spinning wheel from the outside edge, if you try it from further in it gets a lot harder.
I would try the larger discs and standard calipers first and then if you're still not happy upgrade to 4 pot calipers. Larger discs will also dissipate the heat quicker as well so should prevent overheating.
I have some info at home about fitting Porsche Boxster front calipers which I will dig out later for you. It may be overkill and you may well upset the brake balance of the car though.
A good set of fast road pads and 312mm discs should be more than enough to get your abs kicking in, and was good enough for VW to put on their Turbo cars including the 225bhp Audi TT.
Cheers
Paul